ATTEMPTING TO PREDICT THE FATE OF AN ONGOING EPIDEMIC. LESSONS FROM A(H1N1) INFLUENZA IN USA.

An attempt is made to estimate the main parameters of the 2009 Influenza type A(H1N1) outburst in USA based on public information provided by Centers for Disease Control (CDC) during the early stage of the epidemic. Given the ill-posed nature of the statistical problem, a nonlinear fuction estimation method (Gauss-Newton and Hooke Jeeves) was combined with linearization procedures that allowed to set adequate initial guess values for estimation. Based on data until May 13th, 2009, the following values are predicted for the USA outbreak: Tau (time to the peak of incidence) 32 days; R0 (number of secondary infections per infected individual) 1.7; K (total number of cases) 20000(15000-35000). These results are in good agreement with the values reported by the WHO's Rapid Assessment Team for the outburst in Mexico. The method can be applied in any setting where cumulative number of cases are properly recorded